In conventional light emitting diodes (LEDs), a direct current is applied through the device to create excitons in its active region, which in turn are emitted as light. However, when the direct current is applied to the bulk semiconductor material of the LEDs, many of the charge carriers that make up the applied current do not form excitons in the active region of the device. Hence, much of the applied energy is wasted.
Because of the availability and maturity of silicon microelectronics technologies, it would be beneficial to use silicon for the fabrication of optoelectronic devices. Light emission in conventional bulk silicon-based devices, however, is constrained in wavelength to infrared emission, and is inefficient because of the indirect band gap of silicon. Due to its poor light emitting properties, silicon is typically not used to fabricate light emitting devices.
Therefore, it is desirable to provide a silicon or other semiconductor based light emitting device which is very efficient, such that only minimal energy is wasted in constructing the electron-hole pairs that generate the necessary excitons.